This invention relates to a chemical vapor reaction apparatus and a process with uniform irradiation.
It has been proposed to form a conductor, semiconductor or insulator film on a substrate by photo enhanced CVD. For instance, the formation of a silicon or silicon compound film by photo CVD is attracting the interests in the semiconductor field, which is implemented by decomposition of Si.sub.n H.sub.2n+2 (n=1, 2, 3, . . . ) in virtue of the optical energy of ultraviolet light. The thickness of a film deposited by photo CVD depends on the intensity of the incident light. FIG. 1 is a graphical diagram showing the relationship between the intensity of incident light on a substrate to be coated and the thickness of a film thus formed. As shown in this figure, the thickness increases in proportion to the intensity of incident light, and the coefficient is about 0.7.
In prior art, a quasi-uniform irradiation on a substrate has been obtained by arranging a number of lamps on a large area For example, a uniform film with 300 mm in width and 300 mm in length is formed by use of a number of low pressure mercury lamps each having 400 mm in radiation length arranged in parallel with an interval of 400 mm. However, as long as using a definite number of lamps, nonuniformity to the thickness of a film is inevitable.
For this reason, when a more uniform film or a film having a larger area is desired to be coated, the number of lamps has to increase, and therefore the size and the cost of a CVD apparatus are also expanded. The problem arises also in the case of photo-etching, photo-ashing and photo-cleaning.